Literature on creativity stress that it's less about possessing some kind of 'gift' but rather the importance of simply showing up, whether you're feeling inspired or not, and pushing through the resistance to just create something. Anything.
I like to think that Bach's music is evidence of this.
Music theory was much more homogenous then. You could learn everything there was to know in a few years, and after a few more years of work you would be considered competent and ready to enter the job market.
What made Bach different was a long family background of music ('Bach' was practically a synonym for musician in some parts of Germany), and an insane work ethic - he literally walked across Germany to try to get an apprenticeship with a teacher, and he was on top of current developments in the rest of Europe in a way his contemporaries weren't.
But mostly he was a freaking genius - e.g. known for improvising eight-voice fugues, which is something no one else would even consider.
For every discipline there's a certain skill level which no amount of hard work will conquer without a foundation of raw talent - and he lived there.
Another case that I marvel at is Carl Stalling. During the heyday of the Warner cartoon unit he did most of the scores. Yes, yes, not the same as Bach -- Stalling cribbed a lot of well-know music and had access to the Warner music catalog. But the production rate! Imagine: The Warner cartoon studio had 4 units. Each unit did one feature per month, so that they could deliver one new animated short feature every week. Show up Monday with blank paper. Record with the orchestra at a Warner sound stage on Friday. Repeat every week. Wow.
Today, we could write an entire draft novel and discover major plot holes and smooth them out before a single paragraph makes its way into the public eye.
Serial writers have effectively written in stone, and cast their words out to the world. They have to hope they haven’t inadvertently painted themselves into a corner.
Most other composers can benefit from creative interpretation.